<!DOCTYPE html>
<html lang="en">
<head>
  <meta charset="UTF-8">
  <meta name="viewport" content="width=device-width, initial-scale=1.0">
  <title>常见网页布局</title>
  <style>
    div {
      background-color: #ecedf8;
      border: 1px dashed #ccc;
      margin-bottom: 10px;
      text-align: center;
      width: 1226px;
      margin: 0 auto 10px;
    }

    .top {
      height: 100px;
    }

    .banner {
      height: 50px;
    }

    .main {
      height: 400px;
      background-color: #fff;
      border: 0;
    }

    .main .left,
    .main .right {
      float: left;
      height: 400px;
    }

    .main .left {
      width: 300px;
      margin-right: 22px;
    }

    .main .right {
      width: 900px;
    }

    .footer {
      height: 250px;
    }
  </style>
</head>
<body>
  <div class="top">top</div>
  <div class="banner">banner</div>
  <div class="main">
    <div class="left">left</div>
    <div class="right">right</div>
  </div>
  <div class="footer">footer</div>
</body>
</html>